OnePlus explains why OnePlus 5 emergency 911 call bug happened

OnePlus has finally explained what caused a recent bug that prevented some OnePlus 5 handsets from dialling 911.

A software issue that caused select OnePlus 5 handsets to reboot when the USA emergency phone number 911 was dialled was fixed last week, but it wasn’t clear what actually went wrong – until now, anyway.

In a statement, OnePlus has revealed that the bug was caused by a flaw in modem memory usage:

“Last week, we received distressing news regarding an issue related to dialling an emergency number on the OnePlus 5. Late last week an update was released to resolve the issue. We would like to provide additional information on the emergency call issue.”

The spokesperson continued: “The source of this issue was related to a modem memory usage issue that triggered a reboot. This reboot was a random occurrence for some users on VoLTE network where OTDOA protocol was triggered when placing an emergency call.”

According to the statement, OnePlus has worked with Qualcomm to resolve this issue. That’s because the OnePlus 5 uses Qualcomm’s Snapdragon 835 system-on-a-chip, which contains Qualcomm’s own Snapdragon X16 LTE modem.

The OnePlus statement went on: “To clarify, this occurred only on some OnePlus 5 devices, in random instances under the circumstances described above. Starting last Friday, we rolled out a software update that resolved this issue.”

“We took this extremely seriously and want to thank the users who provided device logs to help us quickly resolve it,” it concluded.

The bad news is that it seems possible this bug could affect other devices featuring the Snapdragon 835 chipset or Snapdragon X16 modem. For reference, many popular phones use this chipset, including HTC U11, Sony Xperia XZ Premium, and select versions of the Samsung Galaxy S8.

For this issue to take place, the device needs to be running an X16 modem and the device also needs to be on an LTE network in North America. The device also needs to be in an area where an Observed Time Delay Of Arrival (OTDOA) location service is available and active, triggering the Position Reference Signal (PRS) message from the network. Finally, the device also needs to have a memory map laid out in a way whereby the PRS direct memory access can cross the 64MB boundary.

A source familiar with the matter tells Trusted Reviews that third-party device makers using the Snapdragon X16 modem will have access to the same patch that OnePlus was provided with.